The present invention relates generally to video data transmission, and more particularly to a method and apparatus for streaming scalable video over networks having a variable bandwidth.
Scalable video coding refers to coding techniques that are capable of providing different levels or amounts, of data per frame of video. Currently, such techniques are used by such video coding standards as MPEG-2 and MPEG-4 (i.e. “Motion Picture Expert Groups” coding). In the scalable coding techniques employed by these standards, frames of video data are encoded and divided into a base layer and an enhancement layer.
Typically, the base layer includes a minimum amount of data required to decode the coded video data. The enhancement layer, on the other hand, includes additional data that enhances (i.e. improves the quality of) the base layer when decoded. During operation, all frames of the base layer are transmitted to a receiving device. However, the enhancement layer frames are only transmitted if the receiving device has sufficient processing power to handle the additional frames and/or the medium over which the frames are transmitted has a sufficient bandwidth.
One known scalable video technique is fine-granular scalability. Fine-granular scalability (FGS) codes the same image (e.g., a frame of video) using progressively more data each time coding takes place. For example, in a co-pending application entitled “Scalable Video Coding System,” Ser. No. 09/110,616, to the same assignee as herein, a system is disclosed for video coding that has the property of fine-granular scalability, in which a base-layer of video is coded at a fixed rate, and a residual or enhancement-layer is coded to cover a wide range of rates.
Presently, the ISO MPEG-4 committee is researching methods for fine-granular coding. Thus, a need exists to come up with a practical method for streaming the enhancement layer. In another co-pending application entitled “System for Controlling Data Output to a Network”, Ser. No. 09/177,962, also to the same assignee as herein, a method for streaming data over a packet-based network was disclosed. However, this method was only used in order stream base-layer video over the Internet.